Problem Statement

It is incredibly difficult to find a good source of high purity red iron oxide, Fe2O3, also known as Iron (III) Oxide. I finally discovered that ceramic shops have some pretty good stuff for cheap, but I also wanted to double check and be able to objectively compare between multiple sources.

Visual Inspection

Using a metallurgical darkfield microscope I was able to visually asses the quality as well as particle sizes of the various iron oxide sources. It is clear that some of these sources are just iron rich dirt (iron ore). I was able to overlay a scale bar using mm/pixel data gathered from photographing a rule slide with the exact optical system.

To avoid scrolling, summaries will be posted after the processes are fully described.

Non Acid-Soluble Assay

Sulfuric Acid: I attempted to dissolve the iron early on with sulfuric acid, 35%. However, Iron(III) Sulfate is barely soluble, and therefore only the tiniest amounts were created. Given that H2SO4 is very expensive, and an in solution reducing agent would need to be supplied to continue the dissolution process by converting the Iron(III) to Iron(II) which is highly soluble, the process was abandoned. An avenue of interest is that UV light (sunlight) does appear to photo reduce the Iron(III) to Iron(II), though not quickly enough to aid in timely dissolution.

HCL proved to be far more promising, as both of the oxidation states are highly soluble. Dissolution is rapidly achieved after just 20 minutes of boiling in a 32% solution. HCL is cheap, about $8 a gallon, and easily distilled out again at 20%, unlike sulfuric acid.

Assay Procedure

Measure 2.000g of Sample

Add 25mL HCl (10M) to Sample in a 250mL flask

Boil for 20 minutes

(Optional) Dry filter paper at 105 degrees C

Add 100mL of warm distilled water to the mixture

Tare the filter paper (!)

Filter the sample through the paper, rinsing the sample flask with additional distilled water as needed to capture all sediment.

Note that this is an upper bound to the iron oxide percentage, but could also contain other acid soluble metals and compounds such as nickel, aluminum, copper oxides, etc.

Assay Results

ESKS

Ammonium Nitrate For Sale Dot Com

Because that's not shady at all

Assay:

Not More Than 73% wt% Iron Oxide

Not Less Than 27% wt% Clays / Sands

Alpha Chemicals

Alpha Chemicals Dot Com

Assay:

Not More Than 74% wt% Iron Oxide

Not Less Than 26% wt% Clays / Sands

Prince Agri Products

Repackaged by Custom Feed Services Corp

Claims 50% Iron Min

Assay still in work

Eisen-Golden Laboratories

No website or contact info?!

Claims: "ACS grade" "99.7% purity"

AVOID AT ALL COSTS

Assay:

Not More Than 77% wt% Iron Oxide

Not Less Than 23% wt% Clays / Sands

Majoram Ceramics

Phoenix AZ Location

Assay:

Not More Than 98% wt% Iron Oxide

Not Less Than 2% wt% Clays / Sands

Isolation

In order to isolate the iron from the soil mixtures, we must digest then selectively precipitate out the iron. HCl will ingest metallic iron, iron(II), and iron(III) compounds. UV light will reduce the iron(III) to iron(II). Iron (II) Oxalate is not soluble in water and will precipitate out. Much of the HCl can be recovered and used again in the next cycle.